anthropic-claude-development

SKILL.md

Anthropic Claude API Development

You are an expert in Anthropic Claude API development, including the Messages API, tool use, prompt engineering, and building production-ready applications with Claude models.

Key Principles

Write concise, technical responses with accurate Python examples

Use type hints for all function signatures

Follow Claude's usage policies and guidelines

Implement proper error handling and retry logic

Never hardcode API keys; use environment variables

Setup and Configuration

Environment Setup

import os
from anthropic import Anthropic

Always use environment variables for API keys

client = Anthropic(api_key=os.environ.get("ANTHROPIC_API_KEY"))

### Best Practices

- Store API keys in `.env` files, never commit them
- Use `python-dotenv` for local development
- Set up separate keys for development and production
- Configure proper timeout settings for your use case

## Messages API

### Basic Usage

```python
from anthropic import Anthropic

client = Anthropic()

message = client.messages.create(
    model="claude-sonnet-4-20250514",
    max_tokens=1024,
    system="You are a helpful assistant.",
    messages=[
        {"role": "user", "content": "Hello, Claude!"}
    ]
)

print(message.content[0].text)

Streaming Responses

with client.messages.stream(
    model="claude-sonnet-4-20250514",
    max_tokens=1024,
    messages=[{"role": "user", "content": "Write a story"}]
) as stream:
    for text in stream.text_stream:
        print(text, end="", flush=True)

Model Selection

Use claude-opus-4-20250514 for complex reasoning and analysis

Use claude-sonnet-4-20250514 for balanced performance and cost

Use claude-3-5-haiku-20241022 for fast, efficient responses

Consider task complexity when selecting models

Tool Use (Function Calling)

Defining Tools

tools = [
    {
        "name": "get_weather",
        "description": "Get the current weather in a given location",
        "input_schema": {
            "type": "object",
            "properties": {
                "location": {
                    "type": "string",
                    "description": "The city and state, e.g., San Francisco, CA"
                },
                "unit": {
                    "type": "string",
                    "enum": ["celsius", "fahrenheit"],
                    "description": "The unit of temperature"
                }
            },
            "required": ["location"]
        }
    }
]

response = client.messages.create(
    model="claude-sonnet-4-20250514",
    max_tokens=1024,
    tools=tools,
    messages=[{"role": "user", "content": "What's the weather in London?"}]
)

Handling Tool Calls

import json

def process_tool_use(response, messages, tools):
    # Check if Claude wants to use a tool
    if response.stop_reason == "tool_use":
        tool_use_block = next(
            block for block in response.content
            if block.type == "tool_use"
        )

        tool_name = tool_use_block.name
        tool_input = tool_use_block.input

        # Execute the tool
        tool_result = execute_tool(tool_name, tool_input)

        # Continue the conversation
        messages.append({"role": "assistant", "content": response.content})
        messages.append({
            "role": "user",
            "content": [{
                "type": "tool_result",
                "tool_use_id": tool_use_block.id,
                "content": json.dumps(tool_result)
            }]
        })

        # Get final response
        return client.messages.create(
            model="claude-sonnet-4-20250514",
            max_tokens=1024,
            tools=tools,
            messages=messages
        )

    return response

Vision and Multimodal

Image Analysis

import base64

# From URL
message = client.messages.create(
    model="claude-sonnet-4-20250514",
    max_tokens=1024,
    messages=[{
        "role": "user",
        "content": [
            {
                "type": "image",
                "source": {
                    "type": "url",
                    "url": "https://example.com/image.jpg"
                }
            },
            {
                "type": "text",
                "text": "Describe this image in detail."
            }
        ]
    }]
)

# From base64
with open("image.png", "rb") as f:
    image_data = base64.standard_b64encode(f.read()).decode("utf-8")

message = client.messages.create(
    model="claude-sonnet-4-20250514",
    max_tokens=1024,
    messages=[{
        "role": "user",
        "content": [
            {
                "type": "image",
                "source": {
                    "type": "base64",
                    "media_type": "image/png",
                    "data": image_data
                }
            },
            {
                "type": "text",
                "text": "What do you see?"
            }
        ]
    }]
)

Prompt Engineering for Claude

System Prompts

Be clear and specific about the assistant's role

Include relevant context and constraints

Specify output format when needed

Use XML tags for structured instructions

system_prompt = """You are a technical documentation writer.

<guidelines>
- Write clear, concise documentation
- Use proper markdown formatting
- Include code examples where appropriate
- Follow the Google developer documentation style guide
</guidelines>

<output_format>
Always structure your response with:
1. Overview
2. Prerequisites
3. Step-by-step instructions
4. Examples
5. Troubleshooting
</output_format>
"""

Prompting Best Practices

Use XML tags to structure complex prompts

Provide examples for few-shot learning

Be explicit about what you want and don't want

Use chain-of-thought prompting for complex reasoning

Specify the desired output format clearly

Error Handling

Retry Logic

from anthropic import RateLimitError, APIError
import time

def call_with_retry(func, max_retries=3, base_delay=1):
    for attempt in range(max_retries):
        try:
            return func()
        except RateLimitError:
            delay = base_delay * (2 ** attempt)
            print(f"Rate limited. Retrying in {delay}s...")
            time.sleep(delay)
        except APIError as e:
            if attempt == max_retries - 1:
                raise
            time.sleep(base_delay)
    raise Exception("Max retries exceeded")

Common Error Types

RateLimitError: Implement exponential backoff

APIError: Check API status, retry with backoff

AuthenticationError: Verify API key

BadRequestError: Validate input parameters

Prompt Caching

Using Caching

# Enable caching for frequently used context
response = client.messages.create(
    model="claude-sonnet-4-20250514",
    max_tokens=1024,
    system=[{
        "type": "text",
        "text": "Large context that should be cached...",
        "cache_control": {"type": "ephemeral"}
    }],
    messages=[{"role": "user", "content": "Question about the context"}]
)

Caching Best Practices

Cache large, static content like documentation

Place cached content at the beginning of the prompt

Monitor cache hit rates for optimization

Use caching for repeated similar queries

Message Batches API

Batch Processing

# Create a batch for non-time-sensitive requests
batch = client.messages.batches.create(
    requests=[
        {
            "custom_id": "request-1",
            "params": {
                "model": "claude-sonnet-4-20250514",
                "max_tokens": 1024,
                "messages": [{"role": "user", "content": "Question 1"}]
            }
        },
        {
            "custom_id": "request-2",
            "params": {
                "model": "claude-sonnet-4-20250514",
                "max_tokens": 1024,
                "messages": [{"role": "user", "content": "Question 2"}]
            }
        }
    ]
)

Cost Optimization

Use appropriate models for task complexity

Implement prompt caching for repeated context

Use batches for non-urgent requests

Set reasonable max_tokens limits

Cache responses when appropriate

Monitor token usage patterns

Security Best Practices

Never expose API keys in client-side code

Implement rate limiting on your endpoints

Validate and sanitize user inputs

Log API usage for monitoring and auditing

Follow Anthropic's acceptable use policy

Dependencies

anthropic

python-dotenv

pydantic (for input validation)

tenacity (for retry logic)